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用光镜及电镜研究了原始组织对30CrMnSi加热等温转变过程的影响。结果得出: 退火状态以及淬火並长时间高温回火,α已充分再结晶状态加热时仅形成颗粒状奥氏体γ_(go) γ_g的核沿珠光体团界、珠光体与铁素体界面以及再结晶后的α晶界形成,然后长成γ_(go)在特殊情况下,也有可能长成羽毛状奥氏体。长大过程除受碳在奥氏体中的扩散所控制外,也可能受碳在铁素体中的扩散所控制。淬火状态加热时,可以形成针状奥氏体γ_a及颗粒状奥氏体γ_(go)过热度不大时,以形成γ_为主,仅沿原奥氏体晶界出现细小γ_(go)过热度大时,可全部形成γ_g。,且形核率高,所得组织较细,较退火状态加热所得更细。淬火后的回火能显著降低γ_a与γ_g。的形成速度,尤以γ_g为甚。回火温度愈高,时间愈长,降低愈多。经较长时间高温回火后,γ_g的形成可被充分抑制,仅形成γ_a。如高温回火时间足够长,α已发生再结晶,针状特征已消失,则不再形成γ_a,只能形成γ_(go)。γ_a的形成有孕育期,且随过热度增加而减小,形成速度则随过热度增加而增加。γ_a的核沿板条界在有碳化物处形成。对γ_a与γ_g的形成机构进行了讨论,认为二者都是扩散形核,扩散长大。只是因为形核位置不同,长大条件不同,故长成不同形态的奥氏体。
The effect of primary structure on the isothermal transformation of 30CrMnSi was investigated by light and electron microscopy. The results show that the nuclei that form only granular γ - (go) γ_g of austenite when the α is fully recrystallized exist along the pearlite envelop and the interface between the pearlite and the ferrite interface And recrystallized α grain boundaries, and then grow into γ_ (go) In exceptional circumstances, it is possible to grow feathery austenite. Apart from being controlled by the diffusion of carbon in austenite, the growth process may also be controlled by the diffusion of carbon in the ferrite. When quenching state is heated, acicular austenite γ_a and granular austenite γ_ (go) superheat degree can not be formed, so γ_ (mainly) forms and only small γ_ (go) appears along the original austenite grain boundary. Superheat, can be fully formed γ_g. , And the high rate of nucleation, the resulting tissue smaller, thinner than the annealing state heating. Quenching after quenching can significantly reduce the γ_a and γ_g. The formation rate, especially γ_g is even more. Tempering the higher the temperature, the longer the time, reduce the more. After a long time high temperature tempering, γ_g formation can be fully inhibited, only the formation of γ_a. If the high-temperature tempering time is long enough, α recrystallization has taken place, acicular characteristics have disappeared, then no formation of γ_a, only to form γ_ (go). The formation of γ_a inoculation period, and with the increase of superheat decreases, the formation rate increases with the increase of superheat. The nucleus of γ_a forms at the carbide boundary along the lath boundary. The formation mechanisms of γ_a and γ_g are discussed, and they are considered to be both diffusion nuclei and diffusion growth. Only because of the different nucleation sites, different conditions, grow into different forms of austenite.